Functional Oligomers and Reactive Copolymers for the Generation of Thin Film Nanofoams

A means of generating foams of high temperature polymers, polyimides, has been developed for use in dielectric layers in microelectronics. In these systems, the pore sizes generated were in the tens of nanometers range, thus the term nanofoams. The foams were generated by preparing phase separated block copolymers with the majority phase comprised of polyimide and the minor phase consisting of a thermally labile block. Films were cast, solvent removed and the copolymers are cured, causing phase separation of the two blocks. The labile blocks were subsequently removed via thermal treatments leaving pores the size and shape of the original copolymer morphology. New poly(propylene oxide) (PO) oligomers have been synthesized and used as labile blocks for the formation of polyimide nanofoams. The necessary amine-functionalization of the PO oligomers was achieved by functionalization of hydroxy-terminated PO as well as the direct synthesis of functional PO using a new series of organometallic catalysts. The synthesis of PO oligomers, PO-containing triblock copolymers and the resulting thin film nanofoams were explored.